White blood cell/bone marrow imaging yielded poor diagnosis of chronic shoulder PJI

Grant E. Garrigues, MD

Prosthetic joint infection of the shoulder is a significant challenge due to the lack of a reliable preoperative or intraoperative test to detect infection with Cutibacterium acnes, the most common source of PJI in the shoulder. Thus, we are left relying exclusively on long-hold cultures which have been shown in multiple studies to have a high false-positive rate.

In this current study by Falstie-Jensen and colleagues, researchers utilized a white blood cell/bone marrow single-photon emission (WBC/BM SPECT) CT in a study cohort of 29 patients who had failed arthroplasty and then compared results to biopsy specimens taken during revision surgery. While this technique had previously shown success in the lower extremity, for shoulder PJI, results were disappointing — yielding a sensitivity of only 0.18 despite a specificity of 1 for detection of chronic shoulder PJI. Notably, the test had no ability to detect C acnes.

Unfortunately, the search for a reliable test to detect the presence of a C acnes shoulder PJI must continue as WBC/BM SPECT CT is not the answer. The Danish team should be saluted for a well-done study and now this team and others can set their sights on evaluating the next promising diagnostic tool.

Eric T. Ricchetti, MD

PJI of the shoulder is a diagnostic and therapeutic challenge due to the low virulence of the causative organisms, particularly Cutibacterium acnes (C. acnes). Thomas Falstie-Jensen, MD, and colleagues have investigated the utility of white blood cell/bone marrow single-photon emission CT in the diagnosis of shoulder PJI. The authors found that this test had poor diagnostic performance in a series of 29 patients who underwent revision shoulder arthroplasty. Only two patients had a positive test, and no C. acnes cases had a positive test. Due to these findings and the high cost and resources required to perform the test, the authors concluded that white blood cell/bone marrow single-photon emission CT should not be recommended for use in diagnosis of PJI of the shoulder.

This study is a valuable addition to the literature. No prior study has investigated white blood cell/bone marrow single-photon emission CT in a well-defined revision shoulder arthroplasty cohort and a rigorous definition of shoulder PJI was employed, utilizing standardized tissue sampling and culturing techniques. Such thorough analysis in future studies will lead to further refinement of the optimal diagnostic testing for shoulder PJI.